Information processing device, information processing method, and storage medium

ABSTRACT

An information processing device according to one aspect of the present invention includes at least one memory storing instructions; and at least one processor coupled to the memory and configured to execute the instructions to: extract a candidate point which is a point contributing to a signal at a target point, based on a position of the target point in a three-dimensional space and a shape of an observed object, the target point being a point specified in an intensity map of the signal from the observed object, the intensity map being acquired by a radar; and generate an image indicating a position of the candidate point in a spatial image capturing the observed object.

This application is a National Stage Entry of PCT/JP2017/032973 filed onSep. 13, 2017, which claims priority from Japanese Patent Application2016-183325 filed on Sep. 20, 2016, the contents of all of which areincorporated herein by reference, in their entirety.

TECHNICAL FIELD

The present disclosure relates to processing of data acquired by aradar.

BACKGROUND ART

A technology of observing and analyzing an area to be observed from thesky for the purpose of observing a state of a ground surface and thelike has become widespread.

Synthetic aperture radar (SAR) is a technology of observing a state of aground surface by projecting an electromagnetic wave from the sky andacquiring an intensity of a reflected electromagnetic wave (hereinafteralso expressed as a “reflected wave”). The SAR enables generation of atwo-dimensional map (hereinafter referred to as a “SAR image”) of anintensity of the reflected wave based on a distance between an antennain the sky and an object reflecting the electromagnetic wave. Ingeneration of a SAR image, a position closest to the radar side out ofpoints on a reference plane (for example, a ground surface) isdetermined to be a position of an object reflecting an electromagneticwave. Accordingly, reflection at a point distant from the referenceplane (that is, reflection at a position at a certain altitude) isrecognized as reflection from a position which is different from theactual position and is deviated toward the radar side. Consequently, theimage becomes an image distorted compared with an actual appearance.Occurrence of the distorted image is called foreshortening.

PTLs 1 and 2 disclose a device performing correction processing calledorthorectification in order to correct foreshortening.

PTL 3 discloses a technology of correction for a phenomenon called a“layover” which may be caused by distortion of an image. A “layover”refers to a phenomenon that, when reflection at a point positioned at acertain altitude is recognized as reflection from a position differentfrom a true position, a reflected signal from the point and a reflectedsignal from the different position overlap one another.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No.2007-248216

PTL 2: Japanese Unexamined Patent Application Publication No. 2008-90808

PTL 3: Japanese Unexamined Patent Application Publication No.2008-185375

SUMMARY OF INVENTION Technical Problem

Orthorectification as disclosed in PTLs 1 and 2 does not assumeperforming correction of a SAR image in which a layover occurs.Specifically, orthorectification is correction by which a position of apoint where distortion occurs is shifted to a position estimated to be atrue position. In other words, the orthorectification as described inPTL 1 is processing performed on an assumption that there is onecandidate of a true point contributing to an intensity at a correctiontarget point.

When a correction target point exists in a region where a layoveroccurs, a plurality of candidates of a true point contributing to anintensity at the correction target point may exist. Accordingly, theorthorectification as disclosed in PTLs 1 and 2 does not correct a pointin a region where a layover occurs. PTL 3 discloses a method ofcorrecting a layover by use of a plurality of SAR images. However, thecorrection requires a plurality of differently distorted SAR images.

Thus, without some supplementary information, it is theoreticallyimpossible to isolate reflection positions, which are positions havingreflected the electromagnetic wave of a radar, contributing to a signallying on a point in a region where a layover occurs in a single SARimage.

When a layover is not corrected, that is, when a candidate of areflection point contributing to a signal at a certain point is notnarrowed down, it is a common practice that a person estimates acandidate of a reflection point contributing to the signal on the basisof experience and various pieces of information while viewing a SARimage.

An object of the present invention is to provide a device, a method, anda program that facilitate understanding of a point contributing to asignal at a point in a region where a layover occurs in a SAR image. Inaddition to a SAR image, images used in the present invention mayinclude an image acquired by some other technique for estimating a stateof a target object by observing reflection of an electromagnetic wave,such as an image based on real aperture radar (RAR).

Solution to Problem

An information processing device according to one aspect of the presentinvention includes: candidate point extraction means for extracting acandidate point which is a point contributing to a signal at a targetpoint, based on a position of the target point in a three-dimensionalspace and a shape of an observed object, the target point being a pointspecified in an intensity map of the signal from the observed object,the intensity map being acquired by a radar; and image generation meansfor generating an image indicating a position of the candidate point ina spatial image capturing the observed object.

An information processing method according to one aspect of the presentinvention includes: extracting a candidate point which is a pointcontributing to a signal at a target point, based on a position of thetarget point in a three-dimensional space and a shape of an observedobject, the target point being a point specified in an intensity map ofthe signal from the observed object, the intensity map being acquired bya radar; and generating an image indicating a position of the candidatepoint in a spatial image capturing the observed object.

A program according to one aspect of the present invention causes acomputer to perform: candidate point extraction processing of extractinga candidate point which is a point contributing to a signal at a targetpoint, based on a position of the target point in a three-dimensionalspace and a shape of an observed object, the target point being a pointspecified in an intensity map of the signal from the observed object,the intensity map being acquired by a radar; and image generationprocessing of generating an image indicating a position of the candidatepoint in a spatial image capturing the observed object.

Advantageous Effects of Invention

The present invention facilitates understanding of a point, on anobserved object, which contributes to a signal at a point in a regionwhere a layover occurs in an intensity map of signals that have beenacquired with a radar from the observed object.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a positional relation between asatellite making an observation by SAR and a target object.

FIG. 2 illustrates an example of a SAR image.

FIG. 3 is a block diagram illustrating a configuration of an informationprocessing device according to a first example embodiment of the presentinvention.

FIG. 4 is a diagram illustrating an example of a method of calculating acandidate point.

FIG. 5 is a diagram illustrating another example of a method ofcalculating a candidate point.

FIG. 6 is a flowchart illustrating a processing flow in the informationprocessing device according to the first example embodiment.

FIG. 7 illustrates an example of a SAR image indicating positions offeature points.

FIG. 8 illustrates an example of a spatial image indicating candidatepoints relating to feature points.

FIG. 9 is a flowchart illustrating a processing flow in the informationprocessing device according to the first example embodiment whendesignation of a feature point is received.

FIG. 10 illustrates an example of a spatial image displaying specificcandidate points with an appearance different from that of othercandidate points.

FIG. 11 illustrates an example of an image generated by an imagegeneration unit according to a second example embodiment of the presentinvention.

FIG. 12 illustrates an example of an image displayed by a display deviceaccording to the second example embodiment after designation of afeature point.

FIG. 13 is a block diagram illustrating a configuration of aninformation processing device including a main configuration of theexample embodiments of the present invention.

FIG. 14 is a flowchart illustrating a main operation in the exampleembodiments of the present invention.

FIG. 15 is a block diagram illustrating an example of hardware thatachieves each unit according to example embodiments of the presentinvention.

EXAMPLE EMBODIMENT

Prior to description of example embodiments of the present invention, aprinciple of occurrence of foreshortening in an observation by SAR willbe described.

FIG. 1 is a diagram illustrating a positional relation betweenobservation equipment performing an observation by SAR and a targetobject. For example, SAR is provided by a flying object—such as anartificial satellite or an aircraft—equipped with a radar. A flyingobject equipped with a radar providing SAR moves in the sky, forexample, while maintaining an altitude. An arrow in FIG. 1 indicates atraveling direction of the flying object equipped with the radar, thatis, a traveling direction (also referred to as an azimuth direction) ofthe radar. An electromagnetic wave transmitted from a point S in FIG. 1reflects at a ground surface and a structure M on the ground surface;and part of the reflected wave returns to the radar and is detected.

In FIG. 1, a point Q_(a) is a point on the ground surface, and a pointQ_(b) is a point positioned at a certain altitude on a surface of thestructure M. A distance between the point S and the point Q_(a) is equalto a distance between the point S and the point Q_(b). Further, a lineconnecting the point Q_(b) and the point Q_(a) is perpendicular to thetraveling direction of the radar. In such a case, a reflected wave atthe point Q_(a) is not distinguished from a reflected wave at the pointQ_(b) by the radar. Specifically, an intensity of the reflected wavefrom the point Q_(a) and an intensity of the reflected wave from thepoint Q_(b) are observed in an intermixed manner.

FIG. 2 illustrates an example of an image (hereinafter referred to as a“SAR image”) indicating an intensity distribution of a reflected wavegenerated in such a case. In FIG. 2, an arrow indicates a travelingdirection of a radar. A SAR image is generated on the basis of anintensity of a reflected wave reaching the radar, and a distance betweena point from which the reflected wave is transmitted and the radar.While positions in the traveling direction of the radar can bespecified, reflected waves from two points with an equivalent distancefrom the radar are not distinguished when the two points are equallypositioned with respect to the traveling direction of the radar.Accordingly, while a point P is a point reflecting an intensity of thereflected wave from the point Q_(a), an intensity indicated by the pointP also reflects an intensity of the reflected wave from the point Q_(b).This phenomenon is referred to as a layover. In FIG. 2, a white regionincluding the point P represents a region where a layover occurs. Asolidly shaded region in FIG. 2 represents a region shadowed against theradar by the structure M. This region is also called a radar shadow.

Referring to drawings, example embodiments of the present invention isdescribed in detail below.

First Example Embodiment

First, a first example embodiment of the present invention is described.

Configuration

In the following description, a three-dimensional space serving as areference in processing handling positional information is defined in aninformation processing device 11. A three-dimensional coordinate systemis defined for the three-dimensional space serving as the reference. Thethree-dimensional coordinate system is hereinafter referred to as a“reference three-dimensional coordinate system” or a “referencecoordinate system”. As described later, the reference coordinate systemmay be a geodetic system or a coordinate system of model data 1113 whichare three-dimensional data.

FIG. 3 is a block diagram illustrating a configuration of theinformation processing device 11 according to the first exampleembodiment. The information processing device 11 includes a storage unit111, a feature point extraction unit 112, a geocoding unit 113, acandidate point extraction unit 114, an image generation unit 115, adisplay control unit 116, and a designation reception unit 117. Theinformation processing device 11 is communicably connected to a displaydevice 21.

Storage Unit 111

The storage unit 111 stores data required for processing by theinformation processing device 11. For example, the storage unit 111stores SAR data 1111, a conversion parameter 1112, model data 1113, anda spatial image 1114.

SAR data 1111 are data representing an observation result by SAR.Targets observed by SAR (hereinafter also referred to as “observedobjects”) include, for example, a ground surface and a building. SARdata 1111 are data from which at least a SAR image associated with thereference coordinate system can be generated. For example, SAR data 1111include an intensity for each observed reflected wave, positionalinformation and a traveling direction of a radar when the reflected waveis observed, a distance between a reflection point and the radar, and adepression angle of the radar with respect to the reflection point (anelevation angle of the radar viewed from the reflection point). Thepositional information of the radar may be information described under aso-called geodetic system, such as a longitude, a latitude, and analtitude. The positional information has only to be information by whichcoordinates in the reference coordinate system can be specified.

SAR data 1111 may be a SAR image itself. In that case, the SAR image isassociated with the reference coordinate system.

While SAR data 1111 are used in the description of the present exampleembodiment, observation result data by, for example, real aperture radar(RAR) may be used in another example embodiment.

A conversion parameter 1112 includes a parameter for associating anysignal included in SAR data 1111 with the reference coordinate system.When the reference coordinate system is a geodetic system, a conversionparameter 1112 is a parameter for expressing coordinates of a signalincluded in SAR data 1111 under the geodetic system. For example, whendata of a signal included in SAR data 1111 are expressed by positionalinformation of a radar in the geodetic system and a distance between theradar and a reflection point of the signal, a conversion parameter 1112has only to be a parameter for determining positional information of thereflection point in the geodetic system. When the reference coordinatesystem is not a geodetic system, a parameter for converting betweencoordinates in a geodetic system and coordinates in the referencecoordinate system may be included. That a first coordinate system isconvertible into a second coordinate system is hereinafter described asthat the first coordinate system is “associated with” the secondcoordinate system.

A conversion parameter 1112 may include a parameter for associating acoordinate system of model data 1113 (to be described later) with thereference coordinate system.

Model data 1113 are data for three-dimensionally expressing a shape ofobjects such as a terrain and a structure of a building. Model data 1113is, for example, a digital elevation model (DEM). Model data 1113 may bea digital surface model (DSM) that is data of a surface of the earthincluding a structure or a digital terrain model (DTM) which is data ofa shape of a ground surface. Model data 1113 may separately include aDTM and three-dimensional data of a structure.

Model data 1113 is associated with the reference coordinate system. Inother words, a point in model data 1113 may be described by coordinatesin the reference coordinate system.

A spatial image 1114 is an image capturing a space including an observedobject of SAR. For example, a spatial image 1114 may be any of anoptical image such as a satellite photograph or an aerial photograph, amap, a topographical map, and a computer graphics (CG) expressing aterrain. A spatial image 1114 may be a projection view of model data1113. It is preferable that a spatial image 1114 be an image allowingintuitive understanding of a geographical shape or an arrangement ofobjects in a space presented in the image.

An object or a terrain expressed in a spatial image 1114 is associatedwith the reference coordinate system. Specifically, when any point (atleast a feature point and a candidate point, to be described later) inthe reference three-dimensional space is included in a spatial image1114, a position of the point in the spatial image 1114 is uniquelyspecified. When a spatial image 1114 is an aerial image captured fromthe sky, for example, a relation between a range of the aerial image anda range of the reference three-dimensional space may be alreadyspecified.

A spatial image 1114 may be taken in from outside the informationprocessing device 11 or may be generated by, for example, the imagegeneration unit 115, to be described later, projecting model data 1113.

The storage unit 111 does not always need to hold data inside theinformation processing device 11. For example, the storage unit 111 mayrecord data into a device or a recording medium outside the informationprocessing device 11 and acquire the data as needed. In other words, thestorage unit 111 has only to be configured to acquire data requested byunits in processing in the units, to be described later, in theinformation processing device 11.

Feature Point Extraction Unit 112

The feature point extraction unit 112 extracts a feature point from SARdata 1111. A feature point according to the present disclosure refers toa point extracted as a point which may be focused on in analysis on SARdata 1111. Specifically, the feature point extraction unit 112 extractsone or more points from SAR data 1111 by a predetermined method of pointextraction. A point to be extracted from SAR data 1111 according to thepresent disclosure is a spot corresponding to a point in a SAR image. Inother words, a point refers to a point considered to be a spot fromwhich an acquired signal is transmitted. However, a point may be anaggregate of a plurality of adjacent points (data within a predeterminedrange).

For example, the feature point extraction unit 112 may extract a featurepoint by a technique called permanent scatterers interferometric SAR(PS-InSAR) disclosed in below-described Document 1 and the like.

Document 1: Alessandro Ferretti, et al., “Permanent scatterers in SARinterferometry,” IEEE Transactions on Geoscience and Remote Sensing,vol. 39, no. 1, 2001, pp. 8 to 20, retrieved from the Internet <URL:http://sismologia.ist.utl.pt/files/Ferretti_2001.pdf> (retrieved on Sep.20, 2016)PS-InSAR is a technique of extracting a point where a change in a signalintensity is observed from a plurality of SAR images on the basis ofphase deviations.

Alternatively, the feature point extraction unit 112 may extract a pointsatisfying a predetermined condition (for example, a signal intensityexceeding a predetermined threshold value) input by a person or the likeas a feature point. The feature point extraction unit 112 may extract apoint selected by a determination by a person as a feature point.

The feature point extraction unit 112 transmits information about anextracted feature point to the geocoding unit 113. Information about afeature point includes at least information by which coordinates in thereference coordinate system can be specified. As an example, informationabout a feature point is expressed by positional information (such as alongitude, a latitude, and an altitude) of a radar when a SAR imageincluding the feature point is captured, a traveling direction of theflying object equipped with the radar, a depression angle, and aposition of the feature point in the SAR image or a distance between theradar and the feature point.

Geocoding Unit 113

The geocoding unit 113 assigns coordinates in the reference coordinatesystem to each feature point extracted by the feature point extractionunit 112. For example, the geocoding unit 113 receives information aboutan extracted feature point from the feature point extraction unit 112.On the basis of the information and a conversion parameter 1112, thegeocoding unit 113 specifies a position to which a position of thefeature point corresponds in the reference three-dimensional space.

For example, when the reference coordinate system is a geodetic systememploying an earth ellipsoid, the geocoding unit 113 projects anextracted feature point on a surface (a position at an altitude 0) ofthe earth ellipsoid. A position of a point where the feature point shallbe projected is a position where a distance from the radar is equal to adistance given by the information about the feature point. The geocodingunit 113 specifies coordinates of the projected point. The geocodingunit 113 thus assigns coordinates to the feature point, for example.

Candidate Point Extraction Unit 114

The candidate point extraction unit 114 associates a feature pointassigned with coordinates in the reference coordinate system with apoint (hereinafter referred to as a “candidate point(s)”) relating tothe feature point. A candidate point(s) relating to a feature point willbe described below.

An intensity at a feature point (denoted as a point P) in a region wherea layover occurs may be a sum of intensities of reflected waves at aplurality of points. At this time, a point that may contribute to theintensity at the point P is referred to as a candidate point relating tothe point P in the present example embodiment.

FIG. 4 is a diagram illustrating an example of a method of calculating acandidate point(s) by the candidate point extraction unit 114. FIG. 4 isa cross-sectional view cut out from the reference three-dimensionalspace by a plane passing through a point P and being perpendicular to atraveling direction (azimuth direction) of a radar.

A line GL is a cross-sectional line of a reference plane in thereference three-dimensional space, that is, a plane on which a featurepoint is projected. A line ML is a cross-sectional line of athree-dimensional structure expressed by model data 1113. A point S is apoint indicating a position of the radar. The point P is a point on theline GL such that a distance between the point P and the point S is R.In other words, a position of the point P is a position of coordinatesgiven to the feature point by the geocoding unit 113. When a SAR imageis expressed under the reference coordinate system, a signal of thefeature point is indicated at a position of the point P in the SARimage.

A reflected signal at a point which is on the cross-sectional view andwhose distance to the point S is R is reflected in the intensity at thepoint P. In other words, a point relating to the point P is a point atwhich a circular arc with radius R centered at the point S intersectswith the line ML. When determining points at which the circular arc withradius R centered at the point S intersects with the line ML excludingthe point P is performed as to FIG. 4, points Q₁, Q₂, Q₃, and Q₄ areacquired. In other words, the points Q₁, Q₂, Q₃, and Q₄ are consideredcandidate points.

However, since the point Q₃ is shadowed against the point S (is in aso-called radar shadow), it is not likely that an electromagnetic wavereflected at this point relates to the signal intensity at the point P.Accordingly, the candidate points may be the points Q₁, Q₂, and Q₄excluding the point Q₃. In other words, the candidate point extractionunit 114 may exclude the point Q₃ from the candidate points since asegment connecting the point Q₃ and the point S intersects with the lineML at a point other than the point Q₃.

For example, as described above, the candidate point extraction unit 114extracts candidate points relating to the feature point P. At this time,the candidate point extraction unit 114 may exclude, out of onceextracted candidate points, a point considered not to relate to thepoint P from the candidate points.

Information required for candidate point extraction described aboveincludes a cross-sectional line of model data 1113 by a plane passingthrough the point P and being perpendicular to the azimuth direction inthe reference three-dimensional space, positions of the point S and thepoint P, and a distance R between the point S and the point P.

When the point S is sufficiently distant, electromagnetic waves from thepoint S may be approximated to enter in parallel with an incident lineof an electromagnetic wave into the point P. A method of determiningcandidate points when such an approximation is performed is illustratedin FIG. 5. In this case, candidate points can be specified bydetermining an intersection of a line perpendicular to an incident lineof the radar into the point P and the line ML, on the basis of the pointP. However, since a line parallel to an incident line of the radarpassing through a point Q₃ intersects with the line ML (that is, thepoint is in a radar shadow) in FIG. 5, the point may be excluded fromthe candidate points. In extraction by such a method, accurateinformation about the position of the point S and the distance R is notnecessary. The candidate point extraction unit 114 may calculate aposition of a candidate point by use of, for example, a depression angleθ in place of the position of the point S and the distance R.

The candidate point extraction unit 114 transmits a candidate point(s)relating to a feature point to the image generation unit 115.

When having received designation of a feature point from the designationreception unit 117, to be described later, the candidate pointextraction unit 114 transmits a candidate point(s) relating to thedesignated feature point to the image generation unit 115. Designationof a feature point will be described in detail in a description of thedesignation reception unit 117.

Image Generation Unit 115

The image generation unit 115 generates data of an image which thedisplay control unit 116 causes the display device 21 to display. Forexample, images generated by the image generation unit 115 include a SARimage indicating a feature point and a spatial image 1114 indicating acandidate point(s).

Generation of SAR Image Indicating Feature Point

For example, the image generation unit 115 acquires a SAR image from SARdata 1111 and acquires information about a feature point included in theSAR image from the candidate point extraction unit 114. Then, the imagegeneration unit 115 superimposes a sign (for example, a figure such as acircle) indicating a position of the feature point on the acquired SARimage. Consequently, a SAR image indicating the feature point isgenerated.

A SAR image acquired by the image generation unit 115 may be an imageselected by a viewer or may be a SAR image generated from a range ofdata designated by a viewer. Alternatively, the image generation unit115 may specify a range including every feature point extracted by thefeature point extraction unit 112 and generate a SAR image from SAR data1111 related to the range.

A SAR image may be corrected. Specifically, a SAR image may be an imageindicating signal intensities of SAR data 1111 at positions determinedtaking into account of model data 1113.

Spatial Image Indicating Candidate Point

For example, the image generation unit 115 acquires coordinates of eachcandidate point relating to the aforementioned feature point from thecandidate point extraction unit 114. Then, the image generation unit 115reads a spatial image 1114 including the extracted candidate points fromthe storage unit 111. For example, the image generation unit 115 mayspecify a range in the reference three-dimensional space including theextracted candidate points and select a spatial image 1114 to be read onthe basis of the specified range.

When a spatial image 1114 is an aerial view such as a map or an aerialphotograph, the image generation means may cut out a range includingevery extracted candidate point from the spatial image 1114 and acquirethe cut-out aerial view as a spatial image to be used.

Then, the image generation unit 115 superimposes a display indicatingpositions of the extracted candidate points on the read spatial image1114. Consequently, a spatial image 1114 indicating the candidate pointsis generated.

When superimposing a display indicating the positions of the candidatepoints on the read spatial image 1114, the image generation unit 115 mayspecify the positions of the candidate points by calculation based on aconversion parameter 1112 or the like.

A specific example of specifying a position of a candidate point by theimage generation unit 115 is described.

For example, the image generation unit 115 reads an optical satelliteimage as a spatial image on which a display indicating candidate pointsis superimposed. An optical satellite image refers to an image of aground surface captured from an elevated spot by an imaging device suchas a camera equipped on an aircraft or an artificial satellite.

An optical satellite image may be orthorectified. Orthorectificationincludes a type referred to as true orthorectification and a typereferred to as ground orthorectification.

A true orthorectified image is an image in which not only a terrain butalso a structure is orthorectified. When a spatial image is a trueorthorectified image, a position of a candidate point is a positionwhere coordinates of the candidate point in the reference coordinatesystem is orthogonally projected on a reference plane.

A ground orthorectified image is an image in which a terrain isorthorectified and a structure is not orthorectified. When an opticalimage is a ground orthorectified image, the image generation unit 115determines a position of a candidate point by performing perspectiveprojection with regard to a candidate point positioned on a buildingsurface. However, when the optical satellite image is the one capturedfrom a sufficiently high altitude, the image generation unit 115 mayperform parallel projection in place of perspective projection.

Even when a spatial image is different from the images described above,the image generation unit 115 may calculate a position of a candidatepoint on the basis of association of the spatial image with thereference coordinate system.

When receiving a candidate point relating to a designated feature pointfrom the candidate point extraction unit 114, the image generation unit115 generates a spatial image displaying the candidate point(s) relatingto the designated feature point with an appearance different from thatof other candidate points. For example, a different appearance refers toa difference in color, brightness, size, motion, change of these factorsover time, or the like. As an example, the image generation unit 115 maydisplay the candidate point(s) relating to the designated feature pointin red and the other candidate points in white. The image generationunit 115 may not display the other candidate points and display only thecandidate point(s) relating to the designated feature point.

The image generation unit 115 transmits the generated image to thedisplay control unit 116. An image generated by the image generationunit 115 and an image transmitted by the image generation unit 115 maynot be data in an image format. The generated image and the transmittedimage have only to be data including information required for display bythe display device.

Display Control Unit 116 and Display Device 21

The display control unit 116 causes the display device 21 to display animage received from the image generation unit 115. For example, thedisplay device 21 is a display such as a liquid crystal monitor or aprojector. The display device 21 may have a function as an input unit asis the case with a touch panel. While the display device 21 is connectedto the information processing device 11 as a device external to theinformation processing device 11 in the description of the presentexample embodiment, there may be a mode of the display device 21 beingincluded inside the information processing device 11 as a display unit.In that case, for example, the display unit may be integrated with thedesignation reception unit 117 and provide an input-output function.

Through a display of the display device 21, a viewer viewing the displaygets to know a result of processing by the information processing device11. Specifically, the viewer can observe a SAR image indicating afeature point. Further, a person can view a spatial image displayingcandidate points.

Designation Reception Unit 117

The designation reception unit 117 receives designation of a featurepoint. For example, the designation reception unit 117 recognizes afeature point selected through an input-output device such as a mouse bya person observing a SAR image in which feature points are shown. Whenthe display device 21 has an input function, the designation receptionunit 117 may receive an input given to the display device 21 andrecognize a selection of a feature point on the basis of the input. Thedesignation reception unit 117 receives the recognized feature point asa designated feature point. The designation reception unit 117 mayreceive designation of a plurality of feature points.

The designation reception units 117 convey received designation of afeature point to the candidate point extraction unit 114. Specifically,for example, the designation reception unit 117 transmits informationfor identifying a designated feature point to the candidate pointextraction unit 114. Information for identifying a feature point is, forexample, a numeral or coordinates, associated with the feature point.

The candidate point extraction unit 114 transmits, on the basis ofdesignation of a feature point received from the designation receptionunit 117, a candidate point(s) relating to the designated feature pointto the image generation unit 115. Subsequently, the image generationunit 115 generates a spatial image showing a candidate point(s) relatingto the designated feature point with an appearance different from thatof other candidate points. By the display device 21 displaying thespatial image, a person viewing the display can grasp the candidatepoint(s) relating to the designated feature point.

Operation

An example of a flow of processing by the information processing device11 will be described along a flowchart in FIG. 6.

For example, first, in order to view a SAR image of a specific areabased on SAR data 1111 stored by the storage unit 111, a user selectsthe SAR image included in the storage unit 111.

On the basis of the SAR data 1111 and the like, the feature pointextraction unit 112 extracts a feature point(s) from the selected SARimage (Step S61). The feature point extraction unit 112 transmitsinformation about the extracted feature point(s) to the geocoding unit113.

The geocoding unit 113 assigns coordinates in the reference coordinatesystem to the extracted feature point(s) (Step S62). For example, whenthe SAR image is associated with the reference coordinate system, thegeocoding unit 113 may specify coordinates in the reference coordinatesystem on the basis of a position in the SAR image. The geocoding unit113 transmits the coordinates of the extracted feature point(s) to thecandidate point extraction unit 114.

The candidate point extraction unit 114 extracts candidate pointsrelating to the feature point(s) on the basis of the coordinates of thefeature point(s), model data 1113, and so on (Step S63). In other words,the candidate point extraction unit 114 determines coordinates ofcandidate points (in the reference coordinate system) by the methodalready described. The candidate point extraction unit 114 transmits thecoordinates of the candidate points to the image generation unit 115.

The image generation unit 115 generates a SAR image in which theposition(s) of the feature point(s) is shown and a spatial image inwhich the candidate points relating to the feature point(s) are shown(Step S64).

A SAR image in which positions of feature points are shown is, forexample, an image acquired by superimposing signs indicating thepositions of the feature points on a selected SAR image. FIG. 7illustrates an example of a SAR image in which positions of featurepoints are shown. In the example in FIG. 7, circles representing featurepoints are superimposed on a SAR image in which an intensity isexpressed by a brightness level.

A spatial image in which candidate points relating to a feature point(s)are shown is, for example, an image acquired by superimposing signsindicating positions of the candidate points on a spatial image 1114read from the storage unit 111. FIG. 8 illustrates an example of aspatial image indicating candidate points relating to feature points. Inthe example in FIG. 8, circles representing candidate points aresuperimposed on an optical satellite image capturing a building. Thespatial image may be selected by a viewer. In particular, when a spatialimage 1114 is an optical satellite image, the image generation unit 115may cut out a relevant range to be used from the spatial image 1114 onthe basis of a range of the selected SAR image.

The image generation unit 115 transmits the generated images to thedisplay control unit 116.

The display control unit 116 causes the display device 21 to display theimages generated by the image generation unit 115. Consequently, thedisplay device 21 displays the images generated by the image generationunit 115 (Step S65). For example, the display control unit 116 causesthe display device 21 to display the image in FIG. 7 and the image inFIG. 8 side by side. By viewing this display, a viewer can grasp thecandidate points associated with the feature points in the SAR image.

In the example in FIG. 8, candidate points relating to each of aplurality of feature points are displayed at the same time. A viewer maysend designation of a feature point to the designation reception unit117 in order to distinguish only candidate points relating to a singlefeature point.

FIG. 9 is a flowchart illustrating a processing flow in the informationprocessing device 11 when the designation reception unit 117 receivesdesignation of a feature point.

For example, a viewer selects one of feature points while viewing adisplay such as FIG. 7. A selection method may be a method includingpositioning a cursor at a feature point and clicking a mouse or may be,when a number is assigned to a feature point, a method includinginputting the number. The designation reception unit 117 receives, forexample, such a feature point selection as designation of a featurepoint (Step S91) and transmits information about the selected featurepoint to the candidate point extraction unit 114.

On the basis of the information about the feature point received fromthe designation reception unit 117, the candidate point extraction unit114 specifies candidate points relating to the feature point (Step S92).The candidate point extraction unit 114 may store coordinates ofcandidate points (determined in Step S63) relating to feature pointsalong with a relation to the feature point. When storing the coordinatesand the relation, the candidate point extraction unit 114 has only toread coordinates of candidate points relating to the feature point. Whennot storing the coordinates and the relation, the candidate pointextraction unit 114 may extract candidate points relating to thedesignated feature point again, similarly to the processing in Step S63.

The image generation unit 115 may store a relation between a featurepoint and displayed candidate points. In that case, the candidate pointextraction unit 114 has only to transmit information about thedesignated feature point to the image generation unit 115 (or thedesignation reception unit 117 may transmit the information about thedesignated feature point directly to the image generation unit 115), andthe image generation unit 115 performs the processing in Step S92.

The image generation unit 115 generates a spatial image in which thespecified candidate points are shown with an appearance different fromthat of other candidate points (Step S93). FIG. 10 illustrates anexample of an image generated in this step. In the example in FIG. 10,signs of candidate points other than the designated candidate pointsamong many candidate points are eliminated, and only signs of thedesignated candidate points are superimposed on a spatial image. Theimage generation unit 115 transmits the generated image to the displaycontrol unit 116.

The display control unit 116 causes the display device 21 to display theimage generated by the image generation unit 115. The display device 21displays the image (Step S94). For example, the display control unit 116causes the display device 21 to display the image in FIG. 10 in place ofthe image in FIG. 8. Consequently, a viewer can readily recognizecandidate points on the spatial image relating to the designated featurepoint.

Effect

The information processing device 11 according to the first exampleembodiment enables a viewer to readily understand a point contributingto a signal at a point in a region where a layover occurs in a SARimage. The reason is that the candidate point extraction unit 114extracts a candidate point that is a point possibly contributing to thesignal at a feature point on the basis of model data 1113, and the imagegeneration unit 115 generates an image displaying a position of thecandidate point in a spatial image.

By using model data 1113, the candidate point extraction unit 114 iscapable of calculating candidate points relating to a feature point.Further, excluding a point included in a radar shadow region fromcandidates in a process of extracting candidate points encourages aviewer to more accurately understand candidate points.

Furthermore, reception of designation of a feature point by thedesignation reception unit 117 and display of candidate points relatingto the designated feature point with an appearance different from thatof other candidate points enable a viewer to more readily understand thefeature point.

Second Example Embodiment

The image generation unit 115 may generate a single image displaying afeature point and a candidate point at the same time. A mode in which atype of an image generated by the image generation unit 115 is differentfrom that in the first example embodiment is described below as a secondexample embodiment of the present invention.

The image generation unit 115 superimposes information of SAR data 1111on a spatial image 1114. Specifically, for example, the image generationunit 115 reflects, in a spatial image, signal intensities at pointscorresponding to points in the spatial image. More specifically, theimage generation unit 115 generates an image in which points on aspatial image corresponding to points in the SAR image is processed in adifferent color or the like depending on signal intensities at thepoints. Points on a spatial image corresponding to points in a SAR imagerefer to points considered to contribute to signals at points in the SARdata 1111 (for example, a point closest to a radar (such as the pointQ₁) out of points on a surface of a model by model data 1113). Forexample, the image generation unit 115 generates an image displaying apoint on a spatial image corresponding to a point with a lower signalintensity in the SAR image at a lower brightness level and a point onthe spatial image corresponding to a point with a higher signalintensity in the SAR image at a higher brightness level. The image ishereinafter referred to as a superimposed image.

The image generation unit 115 superimposes signs indicating positions ofcandidate points reflecting signal intensities at extracted featurepoints on the superimposed image, out of candidate points relating tothe feature point. FIG. 11 illustrates an example of an image generatedby the image generation unit 115 according to the present exampleembodiment. Thus, for each feature point, the image generation unit 115generates a display image on which a sign indicting at least oneposition of a candidate point relating to the feature point issuperimposed. In other words, displayed candidate points arerepresentatives of candidate points relating to respective featurepoints. A displayed candidate point is hereinafter referred to as arepresentative point. A number of the representative point does not needto be one for each feature point (for example, the image generation unit115 may display the point Q₁ and the point Q₂ as representative pointsrelating to the point P).

The candidate point extraction unit 114 does not need to extract everycandidate point of the feature point at this point in time. As long asthe candidate point extraction unit 114 extracts at least arepresentative point, the image generation unit 115 can generate theaforementioned image.

The display control unit 116 causes the display device 21 to display thegenerated image.

A viewer selects one or more of displayed representative points. Forexample, the viewer positions a cursor on the displayed image by use ofa mouse. For example, the designation reception unit 117 receives themouse-overed representative point as a designated representative point.The viewer may select (designate) two or more representative points byclicking.

On the basis of information about a point received from the designationreception unit 117, the candidate point extraction unit 114 specifiescandidate points relating to the representative point (Step S92). Acandidate point relating to a representative point specifically refersto a candidate point contributing to a signal intensity exhibited at therepresentative point (Q₁, Q₂, and Q₄ in the example in FIG. 4). Thecandidate point extraction unit 114 transmits information about thespecified candidate points to the image generation unit 115.

The image generation unit 115 generates a superimposed image displayingpositions of the specified candidate points. The display control unit116 causes the display device 21 to display the generated image. FIG. 12illustrates an example of an image displayed by the display device 21.As illustrated in FIG. 12, candidate points relating to a representativepoint on which a cursor is positioned is displayed. Representativepoints other than the representative point on which the cursor ispositioned may be changed to a quiet color as is the case with FIG. 10.

With the configuration as described above, a viewer can readilyrecognize one or more candidate points relating to a feature point on aspatial image and candidate points relating to a selected candidatepoint.

Main Configuration

A main configuration of the example embodiments of the present inventionis described. FIG. 13 is a block diagram illustrating a configuration ofan information processing device 10 including a main configuration ofexample embodiments of the present invention. The information processingdevice 10 includes a candidate point extraction unit 104 and an imagegeneration unit 105.

An example of the candidate point extraction unit 104 is the candidatepoint extraction unit 114 according to aforementioned exampleembodiments. An example of the image generation unit 105 is the imagegeneration unit 115 according to aforementioned example embodiments.

Main processing in each unit in the information processing device 10 isdescribed referring to a flowchart in FIG. 14.

The candidate point extraction unit 104 extracts a candidate point whichis a point contributing to a signal at a target point, on the basis of aposition of the target point in a three-dimensional space and a shape ofan observed object (Step S141). The target point is a point specified inan intensity map of the signal from the observed object. The intensitymap is acquired by a radar. An intensity map of a signal is, forexample, a spatial image on which a SAR image or an observation resultby SAR is superimposed. A point specified in an intensity map isassociated with a point in the three-dimensional space. Examples of thetarget point include a feature point (a point illustrated in FIG. 7)according to the first example embodiment and a representative point (apoint illustrated in FIG. 11) according to the second exampleembodiment. A shape of an observed object is given by model data of athree-dimensional model, for example. The candidate point extractionunit 104 has knowledge about positioning of the three-dimensional modelin the three-dimensional space.

The image generation unit 105 generates an image indicating a positionof the candidate point in a spatial image capturing the observed object(Step S142). Association of a point in the three-dimensional space witha point in the spatial image may be previously performed or may beperformed by the image generation unit 105. In other words, the imagegeneration unit 105 generates an image indicating a position of thecandidate point in the spatial image on the basis of a position of thecandidate point in the three-dimensional space and a relation betweenthe spatial image and the three-dimensional space.

The configuration as described above facilitates understanding of apoint on an observed object contributing to a signal at a point in anarea where a layover occurs in an intensity map of a signal acquired bya radar from the observed object. The reason is that the candidate pointextraction unit 104 extracts a candidate point contributing to a signalat a target point on the basis of model data, and the image generationunit 105 generates an image indicating a position of the candidate pointin a spatial image capturing the observed object.

About Configuration Achieving Each Units

In the example embodiments of the present invention described above,each of components of the devices are denoted as a block on a functionbasis. A part or the entirety of the components of devices is achievedby a possible combination of, for example, a computer 1500 asillustrated in FIG. 15 and a program. The computer 1500 includes, as oneexample, configurations as follows.

-   -   one or more central processing units (CPUs) 1501    -   a read only memory (ROM) 1502    -   a random access memory (RAM) 1503    -   a program 1504A and stored information 1504B to be loaded on RAM        1503    -   a storage device 1505 to store the program 1504A and stored        information 1504B    -   a drive device 1507 that reads from/writes on a recording medium        1506    -   a communication interface 1508 connected with the communication        network 1509    -   an input-output interface 1510 that inputs/outputs data    -   a bus 1511 that connects the components

Each of the components of the devices in the example embodiments areachieved when the CPU 1501 runs the program 1504A achieving functionsthereof after loading the program 1504A onto the RAM 1503. The program1504A that achieves the function of the components of the devices is,for example, preliminarily stored on the storage device 1505 or ROM1502, and the CPU 1501 reads the program when necessary. The program1504A may be supplied to the CPU 1501 via the communication network1509, or may be preliminarily stored on the storage medium 1506, and thedrive device 1507 may read the program and provide the program to theCPU 1501.

The method for achieving each device has various modifications. Each ofthe components of the devices may be achieved by a possible combinationof a separate computer 1500 and a program, for example. In addition, aplurality of components included in the devices may be achieved by apossible combination of one computer 1500 and a program.

A part or the entirety of the components of the devices is achieved byanother general or dedicated circuit, a computer, or a combinationthereof. These may be formed by a single chip, or may be formed by aplurality of chips that are connected via a bus.

When a part or the entirety of the components of the devices is achievedby a plurality of computers, circuits or the like, the plurality ofcomputers, circuits or the like may be arranged in a concentrated manneror may be arranged in a distributed manner. For example, the computers,circuits or the like may be achieved in such a way that each of them isconnected by a communication network, such as a client and serversystem, a cloud computing system or the like.

All or part of the example embodiments described above may be describedas in the following supplementary notes, but the present invention isnot limited thereto.

Supplementary Notes

(Supplementary Note 1)

An information processing device comprising:

candidate point extraction means for extracting a candidate point whichis a point contributing to a signal at a target point, based on aposition of the target point in a three-dimensional space and a shape ofan observed object, the target point being a point specified in anintensity map of the signal from the observed object, the intensity mapbeing acquired by a radar; and

image generation means for generating an image indicating a position ofthe candidate point in a spatial image capturing the observed object.

(Supplementary Note 2)

The information processing device according to Supplementary Note 1,further comprising

designation reception means for receiving designation of the targetpoint selected from target points associated with candidate points,positions of which are indicated by the image generated by the imagegeneration means, wherein

the image generation means generates the image indicating a position ofthe candidate point contributing to the signal at the target pointindicated by the designation in the spatial image, with an appearancedifferent from that of a position of other candidate points.

(Supplementary Note 3)

The information processing device according to Supplementary Note 1 or2, wherein

the radar is a synthetic aperture radar, and

the information processing device further comprises

feature point extraction means for extracting, as the target point, afeature point where a change in an intensity of the signal is observedby a plurality of intensity maps each of which is the intensity map.

(Supplementary Note 4)

The information processing device according to any one of SupplementaryNotes 1 to 3, wherein

the candidate point extraction means extracts, as the candidate point, apoint on a surface of the observed object at a position not being hiddenfrom the radar by the observed object, a distance between the positionand the radar being equal to a distance between the target point and theradar.

(Supplementary Note 5)

The information processing device according to any one of SupplementaryNotes 1 to 4, further comprising

display control means for causing display means to display, side byside, a first image acquired by superimposing a sign indicating aposition of the target point on the intensity map and a second imagegenerated by the image generation means.

(Supplementary Note 6)

The information processing device according to Supplementary Note 5,wherein

the image generation means acquires the spatial image by cutting out arange including the candidate point contributing to the signal at afeature point indicated by the first image from an image capturing theobserved object, and generates an image, as the second image, bysuperimposing a sign indicating a position of the candidate point on thespatial image.

(Supplementary Note 7)

The information processing device according to Supplementary Note 1,wherein

the image generation means generates a display image by superimposing,for each target point, signs indicating positions of one or morerepresentative points out of the candidate points contributing to thesignal at the target point, on a superimposed image acquired bysuperimposing information of an intensity of the signal on the spatialimage,

the information processing device further comprises designationreception means for receiving designation of a representative pointselected from the one or more representative points displayed in thedisplay image, and

the image generation means generates an image by superimposing a signindicating a position of the candidate point contributing to the signalat the representative point designated by the designation, on thesuperimposed image.

(Supplementary Note 8)

An information processing method comprising:

extracting a candidate point which is a point contributing to a signalat a target point, based on a position of the target point in athree-dimensional space and a shape of an observed object, the targetpoint being a point specified in an intensity map of the signal from theobserved object, the intensity map being acquired by a radar; and

generating an image indicating a position of the candidate point in aspatial image capturing the observed object.

(Supplementary Note 9)

The information processing method according to Supplementary Note 8,further comprising:

receiving designation of the target point selected from target pointsassociated with candidate points, positions of which are indicated inthe spatial image; and

generating the image indicating a position of the candidate pointcontributing to the signal at the target point indicated by thedesignation in the spatial image, with an appearance different from thatof a position of other candidate points.

(Supplementary Note 10)

The information processing method according to Supplementary Note 8 or9, wherein

the radar is a synthetic aperture radar, and

the information processing method further comprises

extracting, as the target point, a feature point where a change in anintensity of the signal is observed by a plurality of intensity mapseach of which is the intensity map.

(Supplementary Note 11)

The information processing method according to any one of SupplementaryNotes 8 to 10, comprising

extracting, as the candidate point, a point on a surface of the observedobject at a position not being hidden from the radar by the observedobject, a distance between the position and the radar being equal to adistance between the target point and the radar.

(Supplementary Note 12)

The information processing method according to any one of SupplementaryNotes 8 to 11, further comprising

causing display means to display, side by side, a first image acquiredby superimposing a sign indicating a position of the target point on theintensity map and a second image indicating the position of thecandidate point in the spatial image.

(Supplementary Note 13)

The information processing method according to Supplementary Note 12,comprising:

acquiring the spatial image by cutting out a range including thecandidate point contributing to the signal at a feature point indicatedby the first image from an image capturing the observed object; and

generating an image, as the second image, by superimposing a signindicating a position of the candidate point on the spatial image.

(Supplementary Note 14)

The information processing method according to Supplementary Note 8,comprising:

generating a display image by superimposing, for each target point,signs indicating positions of one or more representative points out ofthe candidate points contributing to the signal at the target point, ona superimposed image acquired by superimposing information of anintensity of the signal on the spatial image;

receiving designation of a representative point selected from the one ormore representative points displayed in the display image; and

generating an image by superimposing a sign indicating a position of thecandidate point contributing to the signal at the representative pointdesignated by the designation, on the superimposed image.

(Supplementary Note 15)

A program that causes a computer to perform:

candidate point extraction processing of extracting a candidate pointwhich is a point contributing to a signal at a target point, based on aposition of the target point in a three-dimensional space and a shape ofan observed object, the target point being a point specified in anintensity map of the signal from the observed object, the intensity mapbeing acquired by a radar; and

image generation processing of generating an image indicating a positionof the candidate point in a spatial image capturing the observed object.

(Supplementary Note 16)

The program according to Supplementary Note 15, further causing thecomputer to perform designation reception processing of receivingdesignation of the target point selected from target points associatedwith candidate points, positions of which are indicated by the imagegenerated by the image generation processing, wherein

the image generation processing generates the image indicating aposition of the candidate point contributing to the signal at the targetpoint indicated by the designation in the spatial image, with anappearance different from that of a position of other candidate points.

(Supplementary Note 17)

The program according to Supplementary Note 15 or 16, wherein

the radar is a synthetic aperture radar, and

the program further causes the computer to perform

feature point extraction processing of extracting, as the target point,a feature point where a change in an intensity of the signal is observedby a plurality of intensity maps each of which is the intensity map.

(Supplementary Note 18)

The program according to any one of Supplementary Notes 15 to 17,wherein

the candidate point extraction processing extracts, as the candidatepoint, a point on a surface of the observed object at a position notbeing hidden from the radar by the observed object, a distance betweenthe position and the radar being equal to a distance between the targetpoint and the radar.

(Supplementary Note 19)

The program according to any one of Supplementary Notes 15 to 18,further causing the computer to perform display control processing ofcausing display means to display, side by side, a first image acquiredby superimposing a sign indicating a position of the target point on theintensity map and a second image generated by the image generationprocessing.

(Supplementary Note 20)

The program according to Supplementary Note 19, wherein

the image generation processing acquires the spatial image by cuttingout a range including the candidate point contributing to the signal ata feature point indicated by the first image from an image capturing theobserved object, and generates an image, as the second image, bysuperimposing a sign indicating a position of the candidate point on thespatial image.

(Supplementary Note 21)

The program according to Supplementary Note 15, wherein

the image generation processing generates a display image bysuperimposing, for each target point, signs indicating positions of oneor more representative points out of the candidate points contributingto the signal at the target point, on a superimposed image acquired bysuperimposing information of an intensity of the signal on the spatialimage,

the program further causes the computer to perform designation receptionprocessing of receiving designation of a representative point selectedfrom the one or more representative points displayed in the displayimage, and

the image generation processing generates an image by superimposing asign indicating a position of the candidate point contributing to thesignal at the representative point designated by the designation, on thesuperimposed image.

The present invention is not limited to the above-described exampleembodiments. Within the scope of the present invention, various changesin form and details that may be understood by a person skilled in theart may be made at embodying the present invention.

The present application claims the benefits of priority based onJapanese Patent Application No. 2016-183325, filed on Sep. 20, 2016, theentire disclosure of which is incorporated herein by reference.

REFERENCE SIGNS LIST

-   10, 11 information processing device-   104 candidate point extraction unit-   105 image generation unit-   111 storage unit-   112 feature point extraction unit-   113 geocoding unit-   114 candidate point extraction unit-   115 image generation unit-   116 display control unit-   117 designation reception unit-   1111 SAR data-   1112 conversion parameter-   1113 model data-   1114 spatial image-   21 display device-   1500 computer-   1501 CPU-   1502 ROM-   1503 RAM-   1504 a program-   1504 b stored information-   1505 storage device-   1506 recording medium-   1507 drive device-   1508 communication interface-   1509 communication network-   1510 input-output interface-   1511 bus

What is claimed is:
 1. An information processing device comprising: atleast one memory storing instructions; and at least one processorcoupled to the memory and configured to execute the instructions to:extract a candidate point which is a point contributing to a signal at atarget point, based on a position of the target point in athree-dimensional space and a shape of an observed object, the targetpoint being a point specified in an intensity map of the signal from theobserved object, the intensity map being acquired by a radar; andgenerate an image indicating a position of the candidate point in aspatial image capturing the observed object.
 2. The informationprocessing device according to claim 1, wherein the at least oneprocessor is configured to execute the instructions to: receivedesignation of the target point selected from target points associatedwith candidate points, positions of which are indicated in the spatialimage, wherein generate the image indicating a position of the candidatepoint contributing to the signal at the target point indicated by thedesignation in the spatial image, with an appearance different from thatof a position of other candidate points.
 3. The information processingdevice according to claim 1, wherein the radar is a synthetic apertureradar, and the at least one processor is further configured to executethe instructions to extract, as the target point, a feature point wherea change in an intensity of the signal is observed by a plurality ofintensity maps each of which is the intensity map.
 4. The informationprocessing device according to claim 1, wherein the at least oneprocessor is further configured to execute the instructions to extract,as the candidate point, a point on a surface of the observed object at aposition not being hidden from the radar by the observed object, adistance between the position and the radar being equal to a distancebetween the target point and the radar.
 5. The information processingdevice according to claim 1, wherein the at least one processor isfurther configured to execute the instructions to cause a display deviceto display, side by side, a first image acquired by superimposing a signindicating a position of the target point on the intensity map and asecond image indicating the position of the candidate point in thespatial image.
 6. The information processing device according to claim5, wherein the at least one processor is configured to execute theinstructions to acquire the spatial image by cutting out a rangeincluding the candidate point contributing to the signal at a featurepoint indicated by the first image from an image capturing the observedobject, and generates an image, as the second image, by superimposing asign indicating a position of the candidate point on the spatial image.7. The information processing device according to claim 1, wherein theat least one processor is configured to execute the instructions to:generate display image by superimposing, for each target point, signsindicating positions of one or more representative points out of thecandidate points contributing to the signal at the target point, on asuperimposed image acquired by superimposing information of an intensityof the signal on the spatial image; receive designation of arepresentative point selected from the one or more representative pointsdisplayed in the display image; and generate an image by superimposing asign indicating a position of the candidate point contributing to thesignal at the representative point designated by the designation, on thesuperimposed image.
 8. An information processing method comprising:extracting a candidate point which is a point contributing to a signalat a target point, based on a position of the target point in athree-dimensional space and a shape of an observed object, the targetpoint being a point specified in an intensity map of the signal from theobserved object, the intensity map being acquired by a radar; andgenerating an image indicating a position of the candidate point in aspatial image capturing the observed object.
 9. The informationprocessing method according to claim 8, further comprising: receivingdesignation of the target point selected from target points associatedwith candidate points, positions of which are indicated in the spatialimage; and generating the image indicating a position of the candidatepoint contributing to the signal at the target point indicated by thedesignation in the spatial image, with an appearance different from thatof a position of other candidate points.
 10. The information processingmethod according to claim 8, wherein the radar is a synthetic apertureradar, and the information processing method further comprisesextracting, as the target point, a feature point where a change in anintensity of the signal is observed by a plurality of intensity mapseach of which is the intensity map.
 11. The information processingmethod according to claim 8, comprising extracting, as the candidatepoint, a point on a surface of the observed object at a position notbeing hidden from the radar by the observed object, a distance betweenthe position and the radar being equal to a distance between the targetpoint and the radar.
 12. The information processing method according toclaim 8, further comprising causing a display device to display, side byside, a first image acquired by superimposing a sign indicating aposition of the target point on the intensity map and a second imageindicating the position of the candidate point in the spatial image. 13.The information processing method according to claim 12, comprising:acquiring the spatial image by cutting out a range including thecandidate point contributing to the signal at a feature point indicatedby the first image from an image capturing the observed object; andgenerating an image, as the second image, by superimposing a signindicating a position of the candidate point on the spatial image. 14.The information processing method according to claim 8, comprising:generating a display image by superimposing, for each target point,signs indicating positions of one or more representative points out ofthe candidate points contributing to the signal at the target point, ona superimposed image acquired by superimposing information of anintensity of the signal on the spatial image; receiving designation of arepresentative point selected from the one or more representative pointsdisplayed in the display image; and generating an image by superimposinga sign indicating a position of the candidate point contributing to thesignal at the representative point designated by the designation, on thesuperimposed image.
 15. A non-transitory computer-readable storagemedium storing a program that causes a computer to perform: candidatepoint extraction processing of extracting a candidate point which is apoint contributing to a signal at a target point, based on a position ofthe target point in a three-dimensional space and a shape of an observedobject, the target point being a point specified in an intensity map ofthe signal from the observed object, the intensity map being acquired bya radar; and image generation processing of generating an imageindicating a position of the candidate point in a spatial imagecapturing the observed object.
 16. The storage medium according to claim15, wherein the program further causes the computer to performdesignation reception processing of receiving designation of the targetpoint selected from target points associated with candidate points,positions of which are indicated by the image generated by the imagegeneration processing, and the image generation processing generates theimage indicating a position of the candidate point contributing to thesignal at the target point indicated by the designation in the spatialimage, with an appearance different from that of a position of othercandidate points.
 17. The storage medium according to claim 15, whereinthe radar is a synthetic aperture radar, and the program further causesthe computer to perform feature point extraction processing ofextracting, as the target point, a feature point where a change in anintensity of the signal is observed by a plurality of intensity mapseach of which is the intensity map.
 18. The storage medium according toclaim 15, wherein the candidate point extraction processing extracts, asthe candidate point, a point on a surface of the observed object at aposition not being hidden from the radar by the observed object, adistance between the position and the radar being equal to a distancebetween the target point and the radar.
 19. The storage medium accordingto claim 15, wherein the program further causes the computer to performdisplay control processing of causing a display device to display, sideby side, a first image acquired by superimposing a sign indicating aposition of the target point on the intensity map and a second imagegenerated by the image generation processing.
 20. The storage mediumaccording to claim 15, wherein the image generation processing generatesa display image by superimposing, for each target point, signsindicating positions of one or more representative points out of thecandidate points contributing to the signal at the target point, on asuperimposed image acquired by superimposing information of an intensityof the signal on the spatial image, the program further causes thecomputer to perform designation reception processing of receivingdesignation of a representative point selected from the one or morerepresentative points displayed in the display image, and the imagegeneration processing generates an image by superimposing a signindicating a position of the candidate point contributing to the signalat the representative point designated by the designation, on thesuperimposed image.